Chemical compounds, such as explosives, chemical warfare agents, and other hazardous materials pose hazards to conventional military forces and to civilian populations, thus making the detection of these compounds imperative. Explosives used in the manufacture of explosive devices, such as Improvised Explosive Devices (IEDs), chemical agents, and many hazardous chemicals, have unique chemical signatures in the electromagnetic-radiation-wavelength range between about 1 and about 4 microns. Therefore, electromagnetic-radiation-based chemical detectors are often used to detect such chemical signatures.
Some conventional electromagnetic-radiation-based chemical detectors used for detecting chemical compounds use expensive and non-uniform mercury cadmium telluride (HgCdTe) detectors, various types of quantum well infrared (QWIP/QWID) photodetectors with special cooling needs, or Indium Gallium Arsenide (InAs—GaAs) or Indium phosphide (InP) based detectors to detect chemical compounds in wavelength region between about 1 and about 4 microns. In addition to high manufacturing costs, the imaging qualities of these detectors are relatively poor, and these detectors require specialized software to accomplish the signal processing.
Another electromagnetic-radiation-based chemical detection technique, up-converts mid-infrared photons to near-infrared photons for detection by standard Charge Coupled Devices (CCDs), which can image into the near-infrared region. Using this technique, electron hole pairs are optically generated. On excitation using an electric field, the holes escape in the near-infrared region, while the electrons escape in the mid-infrared region. Although this approach has unique advantages, it is complex.
Differentiating the unique chemical signatures of target chemical compounds, such as explosives, chemical agents, hazardous chemicals, etc., also presents a problem. For example, many conventional electromagnetic-radiation-based chemical detectors use a grating or a Michelson interferometer to break the electromagnetic radiation over the wavelength region between about 1 and about 4 microns into useful spectra. This approach is impractical for high-speed, high-resolution imaging, however.